High resolution spectroscopy of ultracool M dwarfs

Abstract

(abridged) We present high-resolution echelle spectroscopy of a photometricaly-selected sample if thirty-nine dwarfs with spectral types between M6.5 and L0.5. Two stars, 2MASSI 0253202+271333 and 2MASSW 0952219-192431, are double-lined spectroscopic binaries. We have used our observations to search for Li I 6708 A absorption, characteristic of sub-stellar mass; estimate the level of chromospheric activity through measurement of H-alpha emission fluxes; measure rotational velocities via line broadening; and determine radial velocities and Galactic space motions. Two dwarfs have strong lithium absorption, the previously-known brown dwarf, LP 944-20, and 2MASSI J0335020+234235, which we identify as a probable 0.06 M_sun brown dwarf, age ~1 Gyr. We have investigated the prospect of using the observed frequency of lithium absorption amongst ultracool M dwarfs (M7 to M9.5) as a probe of the initial mass function. The available observations are difficult to reconcile with Salpeter-like power-law mass functions (alpha > 2) for masses below 0.1M_Sun. A comparison between the rotational velocities and -alpha fluxes shows no evidence for significant correlation. Velocity dispersions are significantly lower than those measured for nearby M dwarfs, but show remarkable similarity to results for earlier-type emission-line (dMe) dwarfs. The latter are generally assigned ages of less than ~3 Gyrs.

53 pages, 18 figures Accepted for AJ

References in corpus (25)

• A Non-Gray Theory of Extrasolar Giant Planets and Brown Dwarfs
• The Star Formation History of Field Galaxies
• Sixty-seven Additional L Dwarfs Discovered by the Two Micron All Sky Survey (2MASS)
• New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence
• Keck Spectra of Pleiades Brown Dwarf Candidates and a Precise Determination of the Lithium Depletion Edge in the Pleiades
• The Initial Mass Function of Low-Mass Stars and Brown Dwarfs in Young Clusters
• An Effective Temperature Scale for Late M and L Dwarfs, from Resonance Absorption Lines of CsI and RbI
• A search for L dwarf binary systems
• L Dwarfs and the Substellar Mass Function
• The Discovery of a Field Methane Dwarf from Sloan Digital Sky Survey Commissioning Data
• The Initial Mass Function of Low-Mass Stars and Brown Dwarfs in Taurus
• Four nearby L dwarfs
• Keck Spectra of Brown Dwarf Candidates and a Precise Determination of the Lithium Depletion Boundary in the Alpha Persei Open Cluster
• High-resolution Spectra of Very Low-Mass Stars
• Astrometric radial velocities III. Hipparcos measurements of nearby star clusters and associations
• The orbit of the brown dwarf binary Gl 569B
• The Intermediate Age Brown Dwarf LP 944-20
• From the Top to the Bottom of the Main Sequence: A Complete Mass Function of the Young Open Cluster M35
• Analysis of Keck HIRES spectra of early L-type dwarfs
• Low-mass spectroscopic binaries in the Hyades: a candidate brown dwarf companion
• Light Element Depletion in Contracting Brown Dwarfs and Pre--Main-Sequence Stars
• High-Resolution Spectroscopy of Some Very Active Southern Stars
• Gliese 569B: A young multiple brown dwarf system?
• Effective Temperatures of late L dwarfs and the onset of Methane signatures
• 5-micron photometry of late-type dwarfs

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